Engine Cranks But Won't Start When Cold
The engine cranks normally but fails to start when cold, indicating a likely fuel, spark, or sensor issue. Common causes include a failing fuel pump, faulty coolant temperature sensor, or weak spark.
Diagnosis Details
Possible Causes
Fuel pump check valve failure or weak fuel pressure (loses prime when cold)
Faulty engine coolant temperature sensor (ECT) sending wrong signal to ECU
Weak spark due to worn spark plugs, ignition coil, or crankshaft position sensor
Fuel injector leak or clogged injectors causing poor cold start mixture
Related OBD-II Codes
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What You Should Do
Check fuel pressure at the rail (should hold pressure after key off).
Test ECT sensor resistance and compare to specs.
Inspect spark plugs and ignition coils.
Scan for trouble codes even if check engine light is off.
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Disclaimer: This AI-generated diagnosis is for informational reference only. Always consult a qualified mechanic for an in-person inspection. AutOwner is not responsible for decisions made based on this information.
